From: Michael Ellerman <mpe@ellerman.id.au>
To: Balbir Singh <bsingharora@gmail.com>, linuxppc-dev@ozlabs.org
Cc: duwe@lst.de, linux-kernel@vger.kernel.org, rostedt@goodmis.org,
kamalesh@linux.vnet.ibm.com, pmladek@suse.com, jeyu@redhat.com,
jkosina@suse.cz, live-patching@vger.kernel.org, mbenes@suse.cz
Subject: Re: [PATCH 06/12] powerpc/module: Rework is_early_mcount_callsite()
Date: Thu, 25 Feb 2016 21:28:32 +1100 [thread overview]
Message-ID: <1456396112.15739.7.camel@ellerman.id.au> (raw)
In-Reply-To: <56CE3F25.8030100@gmail.com>
On Thu, 2016-02-25 at 10:39 +1100, Balbir Singh wrote:
> On 25/02/16 01:28, Michael Ellerman wrote:
> > is_early_mcount_callsite() needs to detect either the two instruction or
> > the three instruction versions of the _mcount() sequence.
> >
> > But if we're running a kernel with the two instruction sequence, we need
> > to be careful not to read instruction - 2, otherwise we might fall off
> > the front of a page and cause an oops.
> >
> > While we're here convert to bool to make the return semantics clear.
> >
> > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> >
> Do we even need to do this anymore?
Yes. Otherwise the code in apply_relocate_add() will see a far call with no nop
slot after it to do the toc restore, and it considers that a bug (which it
usually is, except mcount is special).
As we discussed today I'm hoping we can clean this code up a bit more in the
medium term, but this works for now.
cheers
next prev parent reply other threads:[~2016-02-25 10:28 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 14:28 [PATCH 01/12] powerpc/module: Only try to generate the ftrace_caller() stub once Michael Ellerman
2016-02-24 14:28 ` [PATCH 02/12] powerpc/module: Mark module stubs with a magic value Michael Ellerman
2016-02-25 0:04 ` Balbir Singh
2016-02-25 6:43 ` Michael Ellerman
2016-02-25 13:17 ` Torsten Duwe
2016-02-26 10:37 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 03/12] powerpc/module: Create a special stub for ftrace_caller() Michael Ellerman
2016-02-25 0:08 ` Balbir Singh
2016-02-25 10:48 ` Michael Ellerman
2016-02-25 13:31 ` Torsten Duwe
2016-02-26 10:35 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 04/12] powerpc/ftrace: Prepare for -mprofile-kernel Michael Ellerman
2016-02-25 0:28 ` Balbir Singh
2016-02-25 10:37 ` Michael Ellerman
2016-02-25 13:52 ` Torsten Duwe
2016-02-26 10:14 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 05/12] powerpc/ftrace: ftrace_graph_caller() needs to save/restore toc Michael Ellerman
2016-02-25 0:30 ` Balbir Singh
2016-02-25 10:39 ` Michael Ellerman
2016-02-25 14:02 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 06/12] powerpc/module: Rework is_early_mcount_callsite() Michael Ellerman
2016-02-24 23:39 ` Balbir Singh
2016-02-25 10:28 ` Michael Ellerman [this message]
2016-02-25 14:06 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 07/12] powerpc/ftrace: FTRACE_WITH_REGS implementation for ppc64le Michael Ellerman
2016-02-25 0:48 ` Balbir Singh
2016-02-25 15:11 ` Torsten Duwe
2016-02-26 10:14 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 08/12] powerpc/ftrace: Rework ftrace_caller() Michael Ellerman
2016-02-25 1:06 ` Balbir Singh
2016-02-25 14:25 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 09/12] powerpc/ftrace: Use generic ftrace_modify_all_code() Michael Ellerman
2016-02-25 1:10 ` Balbir Singh
2016-02-24 14:28 ` [PATCH 10/12] powerpc/ftrace: FTRACE_WITH_REGS configuration variables Michael Ellerman
2016-02-25 1:11 ` Balbir Singh
2016-02-25 14:34 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 11/12] powerpc/ftrace: Rework __ftrace_make_nop() Michael Ellerman
2016-02-24 14:28 ` [PATCH 12/12] powerpc/ftrace: Disable profiling for some files Michael Ellerman
2016-02-25 1:13 ` Balbir Singh
2016-02-24 23:55 ` [PATCH 01/12] powerpc/module: Only try to generate the ftrace_caller() stub once Balbir Singh
2016-02-25 4:36 ` Balbir Singh
2016-02-25 13:08 ` Torsten Duwe
2016-02-25 14:38 ` Kamalesh Babulal
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